Various contraceptive methods are known for reducing the risk of conception. The condom is a contraceptive method developed for use by men, and is known to reduce the risk of contracting sexually transmitted diseases. Presently, no contraceptive method for use by women is generally known to be effective in reducing the risk of contracting sexually transmitted diseases such as gonorrhea, herpes and more recently, AIDS.
Contraceptive methods currently available to and under the control of women include oral contraceptives, diaphragm, intrauterine devices and vaginal foams, creams and suppositories. Each one of the vaginal formulations utilizes a cytotoxic agent, usually the detergent nonoxynol-9, as active ingredient. A vaginal suppository containing sulphuric acid ester of a polysaccharide (SAEP) in combination with nonoxynol-9 is also known. SAEP is a sulfated polysaccharide with a molecular weight of about 175,000. It inhibits hyaluronidase, an enzyme which is believed to have an indispensable role in fertilization. Nonoxynol-9, if used frequently causes irritation to the mucus membrane of the vagina, inactivates the natural protective vaginal flora and can cause lesions through which an infectious agent can invade and cause infection.
Sexually transmitted diseases, and in particular, AIDS, caused by the Human Immunodeficiency Virus (HIV), present a serious health risk. It is therefore important to develop a method which avoids the vaginal irritation and the nonspecific inactivation of the naturally occurring vaginal microbes while providing protection against infectious microbes and unwanted pregnancies. Several such agents which are noncytotoxic or of low cytotoxicity are known to inhibit HIV infectivity in vitro, such as select sulfated polysaccharides including dextran sulfate and heparin sulfate. Some sulfated polysaccharides are also known to inhibit Herpes Simplex Virus (HSV), including dextran sulfate of relatively high molecular weight. As well, heparin sulfate has been shown to inhibit HSV infectivity. However, these sulfated polysaccharides shown to have anti-viral activity are not known to have contraceptive properties.
Accordingly, there is a need for a contraceptive for use by women, and as an alternative to the use of the condom, which also reduces the risk of contraction of sexually transmitted diseases.